In our fellowship, usually the only thing that people ask about to determine if someone is Christian and part of the body of Christ is, have they been baptized?

There are several problems with this, but the one that comes to mind right now has to do with Mormonism. Mormons baptize. They even immerse and baptize for the forgiveness of sins. Are they therefore Christians and part of the body of Christ?

This is where it becomes clear that it takes more than a simple act of baptism to be a part of the body of Christ. While one does not have to know everything, a biblical understanding of who God is is essential. Mormons have a total different understanding of God. They believe that Christ was a created being, and they do not make him co-eternal with the Father. If your basic conception of God is wrong, as it is with Mormons and Jehovah's Witnesses, then this places a person outside of the orthodox Christian faith. 

Lesslie Newbigin says that when one goes outside of a Christendom context, the doctrine of the Trinity cannot be assumed, and it must be the starting point when explaining who Jesus is.[1] As Christendom continues to fall in the United States, faiths that do not have a Trinitarian understanding of God—such as Mormonism, Islam, and Wicca—continue to grow.[2]

So when we baptize people, we need to help them understand who God is. He is one God, in three persons--the Father, Son, and Spirit. Jesus is the Son of God, co-eternal with the Father and the Savior of the World. 

What understanding do you think people need to have about God, Jesus, and the Holy Spirit when they are baptized? Do you find that most people who are unchurched understand who God is or not?